I'm not sure that applies here. If data is migrated from one app to another, content may change.
We could create a protocol for requesting content-addressable URLs over HTTP, but it wouldn't help with the problem described either.
We could create a protocol for requesting content-addressable URLs over HTTP, but it wouldn't help with the problem described either.
It's more like an API with multiple implementations.
(Even just JSON serialization differences will pop up. For example, PHP always likes to escape forward slashes.)